Furfuryl and tetrahydrofurfuryl derivatives as antiozonants for rubber



United States Patent 3,509,181 FURFURYL AND TETRAHYDROFURFURYLDERIVATIVES AS ANTIOZONANTS FOR RUBBER Frank Aloysius Vincent Sullivan,Westfield, and Tamara Dejneka, Skillman, N.J., assignors to AmericanCyanamid Company, Stamford, Conn., a corporation of Maine No Drawing.Filed May 18, 1967, Ser. No. 639,259 Int. Cl. C07d /04, 5/16 US. Cl.260-3417 5 Claims ABSTRACT OF THE DISCLOSURE A compound of the formula:

wherein R is either furfuryl or tetrahydrofurfuryl and R is phenyl ornaphthyl, or lower-alkyl or lower alkoxy substituted phenyl or naphthyl,or the same as R; and the use of such a compound as an antiozonant inrubber compositions.

This invention relates to the provision of new and useful chemicalcompounds. It relates further to the provision of rubber compositionswhich are resistant to degradation due to ozonation. More particularly,the present invention relates to the provision of phenylene diaminederivatives having one furfuryl or tetrahydrofurfuryl radical on atleast one of the two amino nitrogens, and an aryl radical on theremaining amino nitrogen, each amino nitrogen having a free hydrogen.The use of said compounds as antiozonants in rubber constitutes anotheraspect of the present invention.

It is well-known that natural and synthetic rubber are subject todegradation by atmospheric ozone. Ozone attack is especially pronouncedin rubber vulcanizates which are under stress. In order to inhibit suchdeterioration, it has been common practice to incorporate into therubber stock, prior to vulcanization, any of various compounds whichhave been recognized as possessing antiozonant activity. Among thevarious antiozonants previously used, are, for example,N,N-di-2-octyl-pphenylenediamine,N-phenyl-N'-cyclohexyl-p-phenylenediamine, N,N-bis3-(5-methylheptyl)-p-phenylenediamine and N,N'-di-sec.butyl-p-phenylenediarnine.

An antiozonant must possess certain characteristics to be useful. Ofcourse, it must provide protection against deterioration due to ozoneand preferably be useful in both natural and synthetic rubber. It shouldbe non-toxic under conventional rubber processing conditions and itshould not be a skin irritant. It must have a sufficiently low vaporpressure to remain in the rubber during processing and sufiicientsolubility in the rubber to be able to continually migrate to thesurface which is the situs of the ozone attack. Finally, it should beavailable at a reasonable cost.

It is an object of this invention to provide a new class of usefulcompounds. It is a further object of this invention to provide rubbercompositions which have improved resistance to ozonation. Other objectswill be apparent from the following description of the presentinvention.

The present invention is based upon the discovery of a new class ofcompounds, the members of which possess antiozonant activity in bothnatural and synthetic rubber. These compounds are furfuryl ortetrahydrofurfuryl 3,509,181 Patented Apr. 28, 1970 derivatives ofp-phenylenediamine represented by the following Formula I:

wherein R is a furfuryl or tetrahydrofurfuryl radical and R is aryl orthe same as R. Among the preferred aryl groups have up to two rings andare exemplified by phenyl and naphthyl as well as such groups withlow-alkyl and lower-alkoxy substituents. These compounds satisfy therequirements for antiozonants in rubber.

The novel antiozonant compositions of this invention may be preparedconveniently by the reductive alkylation of p-phenylenediamine or anN-aryl-N-(4-arninophenyl) amine with either furfural ortetrahydrofurfuryl alcohol in the presence of a suitable alkylationcatalyst such as palladium on charcoal, activated Raney nickel, platinumon charcoal, LiAlH NaH, and the like. The reaction conditions used inthe preparation of the compounds of this invention will vary dependingon the facility of the alkylation. Thus, the alkylation may be conductedunder a pressure of hydrogen up to about 3,000 p.s.i.g. or above,-in anautoclave or at low pressure in a Parr Hydrogenator. The reaction may beconducted at a temperature of from about room temperature to about 115C. in the presence of a diluent such as a lower aliphatic alcohol (C toC tetrahydrofuran, etc., or in the presence of an excess of thealkylating agent as a solvent. The amount of catalyst used to effect thealkylation is not especially critical, but will generally be from about0.5% to about 5.0%, based on the total weight of reactants.

The antiozonants of the pesent invention may be used in various ways.The preferred way is to add the antiozonant to the rubber duringcompounding. The antiozonant may also be applied by dipping, painting,or spraying the rubber after it has been vulcanized, although these arenot the most desirable ways to utilize the compounds. The amount ofantiozonant employed may vary from about 0.5 to about 10.0 parts perparts of rubber, but concentrations in the range of about 1.0 to 5.0parts will generally satisfy normal requirements for ozone protection.

It is common practice in the rubber field to incorporate an antioxidantalong wtih the antiozonant since antioxidants are generally inadequateas antiozonants and vice versa. The antiozonants of this invention donot ditfer from other known antiozonants in this respect. Any of thecoventional antioxidants for rubber may be used in the usual amounts inconjunction with the antiozonants herein provided. Such usage may varywidely, of course, and is not a part of this invention.

In addition to natural rubber, the treatmentof synthetic rubber is alsocontemplated by the present invention. The latter include, for example,rubber-like polymers of butadiene-1,3, or substituted butadiene-1,3 andcopolymers thereof with other compounds polymerizable there with.Examples of synthetic rubber-like polymers of butadiene-1,3 andsubstituted butadiene-l,3 are polybutadiene- 1,3, polyisoprene,polychloroprene, and poly(2,3-dimethylbutadiene-1,3). Copolymers includethose of butadiene- 1,3 with polymerizable compounds containing anolefinic (-CH=CH) group, such as styrene, vinyl acetate, vinyl chloride,vinyl naphthalene, acrylic acid and its esters, acrylonitrile,acrylamide, methacrylonitrile and its esters, methacrylamide,methacrylonitrile, isobutylene,

EXAMPLE 1 N,N'-difurfuryl-p-phenylenediamine UCEW NHGEQ Into a 2-literstainless steel autoclave was charged 10.8 parts, 0.1 mole ofp-phenylenediamine and .21 part, .22

, mole of furfural dissolved in 57.6 parts of tetrahydrofuran. To thiswas added 1.0 part of a catalyst consisting of palladium on charcoal.The reaction was carried out for 3.5 hours at a temperature not inexcess of 33 C. and under a hydrogen pressure of 1700 p.s.i.g. max. Thereaction mixture was filtered to remove the catalyst and thetetrahydrofuran stripped off under vacuum. The residue was distilled invacuo. The desired product distilled at 192 C. and 0.05 mm. Hg andcrystallized from heptane, M.P. 64-65 C.

EXAMPLE 2 N,N-ditetrahydrofurfuryl-p-phenylenediamine QCHM NHWO Amixture of 1.1 parts, 0.01 mole of p-phenylenediamine, 6.1 parts, 0.06mole of tetrahyd'rofurfuryl alcohol and 1.0 part of activated Raneynickel was reacted for 15 hours at 185 C. The reaction mixture wasfiltered while still hot and stripped free of unreactedtetrahydrofurfuryl alcohol. There was obtained a 65% yield of desiredproduct, M.P. 45-55 C.

EXAMPLE 3 N-phenyI-N-furfuryl-p-phenylenediamine A mixture of 20.0parts, 0.11 mole of 4-aminodiphenylamine, 9.0 parts, 0.094 mole offurfural was dissolved in 89 parts of tetrahydrofuran. To this solutionwas added 1 part of 5% palladium on charcoal. The reaction was carriedout in a Parr Hydrogenator at room temperature for 1.5 hours under ahydrogen pressure of 40 p.s.i. The reaction mixture was filtered toremove the catalyst and. stripped free of tetrahydrofuran. The desiredproduct was obtained in 92% yield of adequate purity withoutdistillation.

The corresponding N-naphthyl compound is prepared by substitutingN-naphthyl-N-(4-aminophenyl)amine in the procedure of Example 3, for theamine used therein.

EXAMPLE 4 N-phenyl-N'-tetrahydrofurfuryl-p-phenylenediamine A mixture of14.7 parts, 0.08 mole of 4-aminodiphenylamine, 8.45 parts, 0.088 mole offurfural, and 1.0 part of the catalyst of Example 1 was dissolved in35.2 parts of tetrahydrofuran and reacted at 95 C. and a hydrogenpressure of 2500 p.s.i.g. max. until the theoretical amount of hydrogenwas consumed. The reaction mixture was filtered and stripped free ofsolvent to obtain a viscous, dark liquid which was used without furtherpurification.

. 4 EXAMPLE 5 A butadiene-styrene (SBR) formulation was prepared asfollows:

' Parts Baytown 1600 1 150.0 Stearic acid 1.5 Paraffin wax 2.0 Zincoxide 5.0 Sulfur 2.0 Accelerator 2 1.0 Circosol 2-XH naphthenic oil 6.0N-phenyl N tetrahydrofurfuryl-p-phenylenediamine 3.0

Baytown 1600:100 parts cold SBR and 50 parts HAF (furnace black).

2 N-oxydiethylene benzothiazole-2-sulfenamide.

The above composition was cured for 50 minutes at 144.5 C. in the formof a 6" x 6 sheet of 75 mil thickness. Samples from this sheet were thentested by exposure to atmospheric ozone of strips A" x 5% cut from thecured sheet. The strips were secured to a rack which at a predeterminednumber of cycles per minute, stretches and relaxes them, in an attemptto simulate the dynamic flexing of an automobile tire in use. Thesamples were flexed at about 10% and 20% elongations at 6 cycles perminute. Data are shown in the accompanying table.

TABLE I Dynamic ozone N-pheny1-N'-tetraexposure test, hydrofurfuryl-pvisual rating No antiozouant phenylenediamine After 8 hours:

10% No cracks No cracks. 2O Cracked edge Do. After 24 hours:

0 "do Do. 20 2 cracked sides Do. After 32 hours:

10% 2 cracked sides pitted- Do. 20% Cracks on all sides Cracked edge.After 48 hours:

10% do Do. 20% 2 crac ed edges. Modulus at 300% 1,190 1,600.

(imaged). Tensile strength 3,075 3,175.

(imaged). Elongation, percent 600 525.

(Image EXAMPLE 6 A natural rubber formulation was prepared as follows:

Parts Smoked sheets 100.0 Stearic acid 2.0 HAF carbon black 25.0 FFcarbon black 25.0 Zinc oxide 5 .0 Pine tar 3L0 Phenyl-naphthylarnine 1.0BLE-25 1 1.0 Sulfur 2.25 NOBS #1 2 0.5

Nphenyl-N'-tetrahydrofurfuryl-p-phenylenediamine 3.0

BLE 25: A high temperature condensation product of acetone and'diphenylamine.

2 NOBS #1: oxydiethylenebenzothiazole-2-sulf0nanude-10%mercaptobenzothiazolyldisulfide. The above formula was cured 45 minutesat 141 C. Samples were tested as described in Example 5. A compositioncontaining no antiozonant began to show signs of degradation after 8hours exposure and failed after 72 hours. The composition containingN-phenyl-N-tetrahydrofurfuryl-p-phenylenediamine protected the rubbercomposition for 186' hours before failure.

5 6 We claim: 5. The compound of claim 1 which is N-phenyl-N- 1. Acompound of the formula: tetrahydrofurfuryl-p-phenylenediamine.

RHN -R- 1N' References Cited wherein R is either furfuryl ortetrahydrofurfuryl and R 5 UNITED STATES PATENTS is phenyl or naphthyl,or lower-alkyl or lower-alkoxy sub- 3,391,107 7/ 1968 Stahly 260 45-9stituted phenyl or naphthyl, or the same as R.

2. The compound of claim 1 which is N,N-difurfuryl-p- ALEX MAZEL PnmaryExammer phenylenediamine. 10 B. I. DENTZ, Assistant Examiner 3. Thecompound of claim 1 which isN,N'-ditetrahydrofurfuryl-p-phenylenediamine. US. Cl. X.R.

4. The compound of claim 1 which is N-phenyl-N-fur- 260800fuIyl-p-phenylenediamine.

32 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent6,509.18]. Dated April 28, 1970" Invent0r($) Frank Aloysius VincentSullivan and Tamara Dejneka It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 5 "the following example," should read the followingexamples,

Column 5, claim 1, the formula reading smuzn AND swan Alton:

Edward M. Fletcher, Ir. mm I, :0; l Aucmn Officer (iv-1551mmof Patent: J

